This project will evaluate genetic variants within the interleukin 1 (IL-1) gene cluster (IL-1 alpha, beta, IL-1 receptor and IL-1 receptor antagonist) that may impact the presence of alginate-specific opsonic antibody and lack of detectable mucoid Pseudomonas colonization. One factor accounting for heterogeneity in cystic fibrosis (CF) pulmonary disease is suspected to be genetic variation in the IL-1 gene family, which plays a role in mediating innate immunity to P. aeruginosa infection and potentially influences levels of opsonic antibody. Overall, the project will test whether polymorphisms within specific genes in the IL-1 gene cluster represent potential modifying factors that account for phenotypic heterogeneity as measured by the presence or absence of both opsonic antibodies and mucoid P. aeruginosa colonization in CF patients with the ?F508 genotype. A case-control genetic association study design will be used to test for association of variation in the IL-1 gene cluster with the presence or absence of opsonic antibodies and mucoid Pseudomonas. An assessment will then be made on the reproducibility of the genetic associations in two additional family-based CF cohorts. Our unique multicenter collaboration, incorporating CF patients enrolled in the Wisconsin Newborn Screening Program, will ensure needed longitudinal follow-up of young patients necessary to confirm current findings and define complex associations. The resulting data will define the expression of opsonic antibodies in early infections of the CF lung by mucoid P. aeruginosa and the contribution of host response to clinical outcome. This project has several important implications for identification of functional genetic variation in novel molecular targets and development of novel clinical diagnostic and prognostic tools. PUBLIC HEALTH RELEVANCE: Cystic Fibrosis (CF) lung disease is characterized by chronic infection by Pseudomonas aeruginosa and is the major cause of morbidity and mortality in CF patients. The resulting data will define the expression of opsonic antibodies in early infections of the CF lung by mucoid P. aeruginosa and the contribution of host response to clinical outcome. This project has several important implications for identification of functional genetic variation in novel molecular targets and development of novel clinical diagnostic and prognostic tools.